Apparatus for reproducing magnetic information



3 W Lav-M INVENTOR.

S. LEVIN Filed April 21, 1958 HNMb NI APPARATUS FOR REPRODUCING MAGNETIC INFORMATION June 13, 1961 Unite States Patent Filed Apr. 21, 1958, Ser. No. 729,906 '19 Claims. (Cl. 340-174.1)

The invention relates to methods of and apparatus for electronically reproducing signals from magnetic flux patterns recorded on magnet materials having such forms as tapes, sheets, discs, cylinders, or the like. Although the flux fields recorded in magnet mediav are used for examples of the hereinafter description it will be readily seen that fields of such a nature otherwise produced or recorded may also be reproduced by the method of this invention. This application is a continuation in part of application Ser. No. 349,295 filed April 16, 1953, now abandoned.

Practical magnetic media for the purposes of the invention, are generally composed of solid magnet material, comminuted particles of said material dispersed in a carrier element or comminuted particles of said material dispersed in a binder and coated on a non-magnetizable carrier base, or the like. Such layers of magnet material seldom exceed a few thousandths of an inch in thickness and frequently this dimension is about a half a thousandth of an inch. Signals having a representation of an extended image recorded in magnetic materials of such dimensions may have recorded areas comparable with these dimensions. so that the fiux which constitutes the pattern is very small and its density diminishes appreciably at a short distance from the-magnetic material, forming thereby a relatively narrow. surface region in which the flux pattern is concentrated.

It is an object of the invention to provide a pickup device for exploring such magnetic fields and converting said fields to electrical signals for further utilization.

It is another object of the invention to provide a device with which electrons may be given helical, spiral or curved paths when the device is subject to said magnetic .fields so as to indicate the configuration of said fields.

. It is a further object of the invention to provide means for reproducing spaceatime .patterns or images stored in magnetic recordings.

Itis another object of the invention to provide means for reproducing said space-time configurations with high resolution and high percentage ofmodulation.

These and other objects of the invention will be ap .parent from the following description appended claims and drawings in which FIGURE 1 illustrates diagrammatically the emission of electrons from the target when impinged upon by the radiant energy beam and the paths taken by the electrons when brought under the influence of the magnetic pattern record. Also shown are the electron lenses and the beam pick-up arrangement.

FIGURE 2 is a plan view of FIGURE 1 showing a scanning process for sensing a space-time flux configuration record.

FIGURE 3 is another view of FIGURE l'showing an alteration in the scanning beam so as to permit the scanning to proceed by means of the record material alone.

FIGURE 4 is a fragmentary view illustrating an alternative means for providing a beam of electrons adaptable to the arrangement of apparatus shown in FIGURE 1.

FIGURE 5 illustrates an embodiment of the invention wherein the utilization of electron lenses is not required.

FIGURE 6 is an oblique view of a fragment of the tape in FIGURE 1 and shows the flux pattern recorded there- When an electron enters a magnetic field a force is excited on it at right angles both to the field itself and to ice the direction of motion of the electron. This force is proportional to the field strength and to the velocity of the electron. When such a field is uniform and at right angles to the initial path of the electron a circle is described by the electron with a radius proportional to its velocity and inversely proportional to the strength of the field. If the field is sufliciently great in relation to the velocity of the electron the resulting path will be a closed circle in which the electron will continue to revolve until disturbed by some other force. If the field is limited in extent the path of the electron will be a more or less sharply curved arc of a circle according to the strength of the field. If the field is not uniform the path will be a curve of continuously varying radius of curvature. When the incident electron enters the field with a velocity component transverse to the direction of the field, the path will be more complex. The transverse velocity component will give rise to a spiraling displacement and the projection of the path on a plane at right angles to the field will be a circle. When the electron is exposed to the simultaneous action of electric and magnetic fields the total force on it will be the sum of the forces exerted by each field independently and any electron with a transverse velocity component will have a spiral path with a pitch that is determined by the value and polarity of the accelerating potential of the electric field.

It can be seen therefore from the foregoing that electrons which enter or leave a region occupied by a distribution of magnetic flux patterns may readily have their paths altered to such an extent that the new destinations of said electrons Will be considerably displaced from the old, the degree of the displacement being an indication of the nature of the flux patterns. Radial, helical or transverse velocity components which may be developed will aifect the energy distribution of the electrons and any change in energy caused when assuming a new direction will be at the expense of the energy spread in the previous direction.

In the practice of the invention, modulation which is representative of magnetic record fields may be obtained, for example, from (a) arrangements wherein the electrons take a new path on traversing the record fields and continue along the new path until collected (b) arrangements wherein the electrons undergo a change in energy spread upon traversing the record fields and are immediately thereafter collected (0) arrangements wherein the electrons take a new path on traversing the record fields, travel along the new path for a substantial distance and are then focused or deviated by other fields and then collected (d) arrangements having a focal system of which the emission element is a part and the record signal fields are at an object focal point and wherein the electrons upon traversing the signal fields undergo a change in energy spread proportional to the signal fields but remain thereafter within the focal system until collected (e) arrangements having a focal system in which a first pick-up electrode is at an image point and wherein the electrons traversing the record signal fields undergo a change in direction whereby the image is displaced from the first pick-up electrode and lands on a second pick-up electrode (1'') arrangements with collectors which have a resistive gradient from any one point to any other point thereof or said resistive gradient property in combination with the collectors of (a), (c) or (d) above. 7

FIGURE 1, by way of example, illustrates an embodiment of the invention in which reference number 56 indicates an evacuated envelope of glass or other suitable material enclosing a pick-up electrode 57 preferably but not necessarily in the form of an electron multiplier, a conductive pick-up electrode 58, an accelerating electrode 61 comprising one or more metallic cylinders or a film-like deposit applied in a conventional manner directly to the inner surface of envelope 56, and an extended target elec trode 47"for example a photocathode, deposited in any well known manner on the inner surface of end wall 70 and adapted for the emission of electrons when impinged upon by a beam of light or other radiant energy beam.

The end wall 70 may also serve as the target electrode 47 by being constructed of a conductive material sealed into the envelope 16 in a manner to have a surface exterior to and a surface interior to the envelope 16, and may be comprised of, for example, non-magnetic materials such as brass, copper, tin or the like or magnetic materials such as nickel, iron, permalloy or the like. It is also desirable, in accordance with the invention to keep the thickness of the end wall 70 to as small a dimension as possible when using either magnetic or non-magnetic materials. A suitable thickness range, for example, is from .0005 inch to .015 inch and will provide a practical device if sealed, in any conventional manner, over a narrow slit in the envelope 16, the slit, for example, being from .25 mm. to 1 mm. long and a width approximately equal to the width of the tape 30. When utilizing this type of construction, the slit is scanned by the beam 20 along its width. A particularly suitable sheet of magnetic material for covering the aforementioned slit is, for example, an alloy of 78% nickel and 22% iron, heat treated in pure dry hydrogen with a magnetic field normal to its surface. A field of 15 oersteds at a temperature of 1400 degrees centigrade, for example, will cause a preferred magnetic axis to form in the end wall 70 in the direction of this field. The recorded fields of the tape 30 in juxtaposition with the end wall 70, instead of spreading out, are confined along this oriented magnetic axis and appear at the inner surface of the end wall 70 with substantially the same characteristics that are found at the surface of the tape 30.

In accordance with the invention radiant energy is construed to relate to radiation not only from the visible portion of the electromagnetic spectrum but also in infrared rays, ultra-violet rays, gamma rays and the like.

Disposed about the envelope 56 is the coil 62 which, with the electrode 61, comprises an electron lens capable of forming an image of target electrode 47. This lens coil 62 may be constructed as a long solenoid extending from the target 47 to the pick-up electrode 58 producing a field which causes the electron beam paths to be characterized by nodes and antinodes and having unity magnification or it may be constructed as a short lens, a coil that is thin in comparison to the distance between the target 47 and the pick-up electrode 58, forming thus a real image with variable magnification. The field of such a lens extends around its equatorial mid plane and decays on either side of this mid plane. When utilizing a short lens, the pick-up electrode 58 may be positioned, for example in the region of said mid plane of the lens or may be positioned at the cross-over of the beam 59 in the image plane. The pickup electrode 58 may be positioned, for example, in the region of an image plane when utilizing the coil 62 as a long lens. The field strength of the coil 62 may be varied by the control 71 and direct current supply.

Biasing voltages for the electrodes 47, 57, 58 and 61 are obtained from voltage divider 64 and the pick-up electrode 57 is coupled to video load circuit 65.

In close proximity to or in contact with end wall 70 is magnetic material '30 having configurations recorded thereon in the form, for example, of a flux pattern 35 as shown in FIGURE 6 and forming a flux image on target 47.

The target 47 is scanned (by means not shown) by radiant energy beam 48 through the window in short neck 66 of the envelope 56 in any predetermined manner. The beam 48 may be produced by the radiant energy screen of a conventional cathode ray tube having scanning features and conveyed to the target 47 by optical means.

As electrons are emitted from target 47 they are accelerated into a field of coil 62 by electrode 61 to form beam 59 indicated in FIGURE 7 by the solid lines. The

biasing potentials on electrode 61 and pick-up electrode 58 are adjusted by potentiometric controls 72 and 73 respectively at the same time and focus of coil 62 is varied by means of control 71 so that all of beam 59 lands upon pick-up electrode 58. The accelerating potential of the electrode 61 is adjusted so that the electrons are substantially influenced by it only after having traversed the flux pattern 35. Since the magnetic field of the coil 61 decays rather rapidly on either side of its equatorial mid-plane, the field may be adjusted so that it will affect only a segment of the electron path between the target 47, the pick-up electrode 57 and the pick-up electrode 58. If, as stated previously, the, pick-up electrode 58 is constructed so as to be at a position, for example, in the region of the equatorial mid plane of a thin lens, beam 59 will not leave the pick-up electrode 58 for any change of position of radiant energy beam 48 while scanning the target 47. This is the zero modulation adjustment and is made when no flux pattern 35 is recorded on magnet material 30. Since none of the electrons .of beam 59 are able to reach pick-up electrode 57, no signal appears at the output of video load circuit 65. When a flux pattern 35 appears on magnetic material 30, the electrons being emitted by target 47 and which previously formed beam 59, take a new series of paths due to the. helical velocity components developed in traversing flux pattern 35 and shift from pick-up electrode 58 as a function of the strength of said helical components. These new paths are shown by the dashed lines '60 which are but a few examples of the multiplicity of paths that might be taken. The electrons thus displaced from pick-up electrode 58 land on pick-up electrode 57 and there will appear at the output of video circuit 65 a signal modulated as a function of the magnetic flux representing the image signals recorded on magnetic material 30.

Pick-up electrode 57 is shown in FIGURE 1 in a position behind pick-up electrode 58 mainly for the purposes of clarity and may be provided with an aperture and positioned, for example, circumferentially by passing or in front of target electrode 58.

FIGURE 2 is a plan view of FIGURE 1 showing how pick-up electrode 58, if constructed in a position at the crossover point at the mid plane always receives beam 59 during the scanning process when no signal flux is present on magnet material 30. Indicated by X are several diverse points in the scanned path at which radiant energy beam 48 impinges on target 57 to release the electrons which form beam 59.

Pick-up electrode 58 alone may be. utilized to obtain a modulated output. When it is positioned in the midplane of the fields of the focusing system elements 61 and 62, with video circuit 65 connected to it and with operating conditions adjusted so that the target electrode is always at the object focal point it will be found that substantial modulation is available. The electrons comprising beam 59, after traversing flux pattern 35 will travel along the force field lines of the focal system until collected by pick-up electrode 58. Since the radial, helical or transverse velocity components developed by the electrons on traversing the flux pattern 35 will change the energy spread of the electrons in proportion to the strength of said flux, the out-put signal from the electrode 58 is an intensity modulated representation of the tape record.

The pick-up electrode 58, with the video circuit 65 reconnected to it, may also be placed, as another example, at the crossover of the beam 59 in the image plane and an electron image of target 47 will be focused thereon. The pick-up electrode 57 is not utilized here. As the beam 48 scans the target 47, the electron beam 59 will scan the pick-up electrode 58. The voltage divider slider 73 makes contact with the pick-up electrode 58 as shown in FIGURE 1 and the contact is made along the full length of the scanned path. As fields appear on the tape 30, the beam 59 undergoesa helical shift in function of the fields, it is deviated fromitsinitial scanningpath but does not r leave the pick-up electrode 58. To obtain modulation, the ohmic resistance gradient on either side of the slider 73 connection to the electrode 58 is utilized. The greater the distance from the connection the greater the resistance and the lower the output from circuit 65. Constructing the electrode 58 of, for example, a thin carbon plate or a sheet of nickel-chromedron will provide a steeper resistance gradient and greater incremental change in the beam 59 currents.

FIGURE 3 is an arrangement in accordance with the invention in which radiant energy beam 48 is spread out to form beam 59 in the shape of a thin wedge which simulates a slit and is held stationary. Only magnetic material 30 passes the target 47.

FIGURE 4 is an arrangement in accordance with the invention and a variation of the device illustrated in FIG- URE l in which radiant energy beam 48 is replaced by electron beam 50 formed and directed by the cathode ray gun comprising electrodes 53, 54, 55 which are sealed into envelope 56 at short neck 66. Coils 52 deflect electron beam 50 in any predetermined manner. Electron beam 50 impinges upon target 51 which is adapted in any well known manner for the emission of secondary electrons and which is substituted in place of target 47 at end wall 70. It is well known in the art that secondary electrons are emitted with a cosine distribution for any incident angle of the primary electron beam and that the velocities are low. Well known too, is the fact that the production of secondary electrons is attendant with the elastic and inelastic scattering or reflecting of the primary electrons at comparatively high velocities and it has been shown that such primaries do not have a cosine distribution of emission but tend to take paths similar to the angle of the primary beam and at substantially the same velocity.

The incident beam 50 impinges the target51 at a considerable angle. The power of the lens elements 62 and 72is adjusted so that the secondary emission forms beam 59 which is focused on the pick-up electrode 58. The scattered and reflected primaries are unafiected by the lens because of high velocities. Because of the beam 50 angle, reflected primaries are in the greatest number at an angle similar to the primary beam 50, but away from it, landing on the accelerating electrode 61. .The scattered primaries are more diffuse and having high velocities are not easily focused when the electron lens is adjusted for focusing the secondaries, therefore very few of the scattered primaries reach the electrode 58. The primary beam 50 velocity should be set high enough so that the beam 50 is unaliected by the fields of the tape 30, as the resolution would otherwise be degraded. The secondary beam 5,9.is modulated in function of the fields 35 of tape 30 as described hereinbefore.

By adapting the target 51 to be at a substantially zero or slightly negative voltage, the velocity of beam 50 will be reduced to a very low value as it approaches the target 51 and then will be totally reflected away therefrom and into the electron lens and pick-up arrangements which have been described hereinbefore. Since the incident beam does not land on target 51 it is obviousthat scattered and reflected primaries are non-existent in this mode of operation.

The example as given in FIGURE 1 may be'modified in accordance withthe invention by a construction of the device that eliminates pick-up electrode 57 and accelerating electrode 61 and coil 62.

In FIGURE 5 is shown such as embodiment wherein the envelope 56 is constructed of a material transparent to" the radiant energy beam 48 which impinges upon the target 47. The pick-up electrode 58 may be deposited in any well known manner on the end wall 70 as shown in FIG- URE 5 or may be positioned elsewhere within the envelope 56. The target electrode 47 is connected to the negative terminal of the voltage divider 64 and the pick-up electrode 58 is connected to movable connection 73. The video load circuit 65 is connected to the pick-up electrode 6 58. The beam 48 may scan the target 47 in a manner as described in FIGURE 1. When no magnetic pattern 35 exists on the tape 30 the electron beam 59 lands on the pick-up electrode 58. As the magnitude of the magnetic pattern 35 changes, the electron beam 59 changes position, as for example to beam 60 thereby the pick-up electrode 58 receives less emission from the target electrode 47. Thus amodulated signal representative of the magnetic patterns 35 may be obtained from the video circuit 65.

By adjustment of the potential on the pick-up electrode 58 all of beam 59 may be made to land on said pick-up electrode 58 for all magnitudes of the magnetic pattern 35. The total kinetic energy of the beam 59 at any point is determined by the space potential at that point. Since the helical energy is acquired at the expense of the longitudinal energy the space potential is increased and the beam current decreased. Therefore the helical co'riipo'- nents caused to be developed in beam 59 as a function of the magnetic pattern 35 provide a modulation representative of the configuration of the pattern 35. The pick-up electrode 58 may be adapted to have a substantial ohmic resistance gradient as described in FIGURE 1 by being deposited as a thin film, for example, of carbon. Any deviation of the beam 59 across the electrode "58 will provide a greater incremental change in the beam 59 currents. By a further adjustment of the potential on the pick-up electrode 58, the modulation produced by the transfer of longitudinal energy to the helical energy may be reduced to zero and the modulation may occur by means of the incremental change in beam 59 current caused by the resistive gradient of the electrode58'5 In FIGURE 6 is shown a fragment of the tape 30 showing an example of a pattern of magnetic fields which may be utilized with the invention. I i

Electrostatic electron lenses may be utilized for any of the constructions hereinbefore described with substantially the same results. 7 f

Although a target adapted for the emission of electrons when impinged upon by a beam of radiant en'ergyand electrons emitted by secondary emission have been as examples in the foregoing as sources of electrons, other sources such as field or cold emission, or thermionic emission may be used with arrangements in accordance with the invention. I

What is claimed is: if

1. An apparatus for translating magnetic signals to electrical signals which comprises an envelope, a target means positioned in a predetermined area of said envelope, said target means having a face, said face being adapted for the emission of a stream of electrons when, impinged upon by a beam of radiant energy, means for forming and conveying said beam of radiant energy to said face, means for positioning a magnetic condition record so as to cause its magnetic fields to permeate said target means and estab lish a pattern of magnetic fiields on said face, rneans for subjecting said radiant energy beam to consecutive areas of said face whereby the electrons of said stream alter their paths in dependence on the magnetic condition of said pattern of fields, means for collecting and means for utilizing the so deviated electrons.

2. An apparatus as claimed in claim 1 wherein said collecting means comprises a pick-up electrode adapted to receive said electrons for all states of interaction of said electrons with said magnetic fields.

3. An apparatus for translating magnetic signals to electrical signals as claimed in claim 2 wherein said collecting means is adapted to have a resistive gradient across its area whereby a change in the current of said electron stream is produced for any change of its position on said collecting means.

4. An apparatus as claimed in claim 1 wherein said collecting means comprises a pick-up electrode adapted to receive said electrons when no fields exist on said magnetic space pattern record but not receiving said electrons in function of the degree of interaction of said electrons with said fields when they exist on said magnetic space pattern record. V r

' 5. An apparatus for translating magnetic signals .to electnical signals as claimed in claim 1 wherein there is ineluded electron lens means for producing electromagnetic and/ or electrostatic fields for focusing and directing said stream of electrons from said target means to said collecting means.

6. An apparatus for translating magnetic signals to electrical signals which comprises an envelope, a target means sealed into a predetermined area of said envelope, said face being adapted for the emission of a stream of electrons when impinged upon by a beam of radiant energy, means for forming and conveying said beam of radiant energy to said face, a magnetic condition space pattern record, means for positioning said magnetic condition space pattern record at the exterior of said target means so as to cause its magnetic fields to permeate said target means and establish a space pattern of magnetic fields on said face, means for subjecting said emitted electrons to consecutive areas of said magnetic fields of said space pattern whereby said' emitted electrons take curved paths traversing said magnetic fields Whereby said curved paths vary in function of the magnetic condition of said space pattern, electron lens means for providing a plane in which said face is imaged by said electron stream, a collecting means positioned at said image plane, said collecting means being adapted to have .a resistive gradient across its area whereby a change in the current of said electron stream is produced for a change of the position of said electron stream on said collecting means.

7. An apparatus for translating magnetic signals to electrical signals which comprises an envelope, a target electrode sealed into a predetermined area of said envelope, means for disposing a magnetic space pattern record at the exterior surface of said target electrode in a manner to permeate and establish a space pattern of magnetic fields on the interior surface thereof, said interior surface being adapted for the emission of electrons when impinged upon by rays of radiant energy, means, including said rays of radiant energy for subjecting consecutive portions of said space pattern of magnetic fields to said electrons, means for focusing and directing said electrons from said target electrode to a collecting means, said means for focusing and directing said electrons providing a nodal region which said electrons traverse and a plane in which said target electrode is imaged thereafter by said electrons, a first pick-up electrode positioned in said nodal region, said focusing and directing means are adapted to cause said electrons to land on said first pick-up electrode when said electrons are not affected by said space pattern of magnetic fields and a second pick-up electrode is positioned to receive the electrons caused to be displaced from said first pickup electrode in function of the magnetic characteristics of said space pattern, said second pick-up electrode comprising an electron multiplier.

'8. An apparatus for translating magnetic signals to electrical signals which comprise an envelope, target means sealed into a predetermined area of said envelope, said target means having a face within said envelope said face adapted for the emission of a stream of electrons when impinged upon by a beam of radiant energy, means for forming and conveying said beam of radiant energy to said face, means for positioning a magnetic condition space pattern record so that its magnetic fields permeate said target means and establish a space pattern or magnetic fields on said face, means for subjecting said emitted electrons to consecutive portions of said magnetic fields of said space pattern whereby the paths of said emitted electrons are deviated in function of the magnetic condition of said space pattern of fields, electron lens means for focusing and directing said deviated electrons,".a first collecting means, said electron lens adapted to include a magnetic field which occupies a portion of the area-between said target means and a second collecting means, said first collecting means being posi: tioned in the equatorialmid-plane of said magnetic field ofsaid electron lens, said first collecting means and electron lens being adapted to land said emitted electrons of said first collecting means when said emitted electrons are not affected by said space pattern of magnetic fields, said second collecting means being adapted to receive the electrons caused to be displaced from said first collecting means in function of the magnetic conditionof said space pattern of fields.

9. An apparatus for translating magnetic signals to electrical signals which comprises an envelope, a target means sealed into a predetermined area of said envelope, said target means having a face within said envelope, said face being adapted for the emission of a stream of electrons when impinged upon by a beam of radiant energy, means for forming and conveying said beam of radiantenergy to said face, a magnetic condition space pattern record, means for positioning said magnetic condition space pattern record at the exterior of said face, said target means comprised of a sheet of magnetic material adapted to have an oriented magnetic structure by means of which the fields of said space record are established on said face, means for subjecting said radiant energy beam to consecutive areas of said face whereby said emitted electrons take helical paths in dependence on the magnetic condition of said space pattern of fields, electron lens means for providing a plane in which said face is imaged by said electron stream, 'a first collecting means positioned in said image plane, said first collecting means and said electron lens adapted to land said emitted electrons on said first collecting means when said emitted electrons are not affected by said space pattern of magnetic fields and a second collecting means positioned to receive the electrons caused to be displaced from said first collecting means in function of the magnetic condition of said space pattern of fields, said second collecting means comprising an electron multiplier.

10. An apparatus for translating magnetic signals to electrical signals which comprises an envelope, a target means sealed into a predetermined area of said envelope, said target means having a face within said envelope, said face being adapted for the emission of secondary electrons when impinged upon by a primary beam from a cathode ray gun within said envelope, a magnetic condition space pattern record, means for positioning said magneticcondition space pattern record at the exterior of said target means so as to cause its magnetic fields to permeate said target means and establish a space pattern of magnetic fields on said face, means for subjecting said primary beam to consecutive areas of said face whereby said secondary electrons alter their paths in dependence on the magnetic condition of said space pattern of fields, means for separating said secondary electrons from the scattered and reflected primary electrons, means for collecting said so deviated secondary electrons and means for utilizing said collected electrons.

11. An apparatus for translating magnetic signals to electrical signals as claimed in claim 10 wherein electron lens means are provided for focusing and directing' said deviated secondary electrons from said face to said collecting means.

12. 'An apparatus for translating magnetic signals to electrical signals as claimed in claim 10 wherein means are provided for collecting said scattered and reflected primary electrons.

13. An apparatus for translating magnetic signals to electrical signals which comprises an envelope, a target means sealed into a predetermined area of said envelope, said target means having a face within said envelope, said face being adapted for the emission of a stream of electrons when impinged upon by a beam of radiant energy, means-for positioning a magnetic condition space pattern record at the exterior of said target means, said target means comprised of a sheet of magnetic material adapted to be magnetized by said record whereby a space pattern of magnetic fields is established on said face, means for forming and conveying said beam of radiant energy to said face, means for subjecting said radiant energy beam to consecutive areas of said face whereby the electrons of said stream alter their paths in dependence on the magnetic condition of said space pattern of fields, means for collecting and means for utilizing the so deviated electrons.

14. An apparatus for translating magnetic signals to electrical signals which comprises an envelope, a target means sealed into a predetermined area of said envelope, means for disposing a magnetic space pattern record at the exterior surface of said target means in a manner to permeate and establish a space pattern of magnetic fields on the interior surface thereof, said interior surface being adapted for the emission of a stream of electrons when impinged upon by a beam of radiant energy, means for forming and conveying said beam of radiant energy to said interior surface, means for subjecting said radiant energy beam to consecutive areas of said interior surface whereby the electrons of said stream alter their paths in dependence on the magnetic condition of said pattern of fields, means for collecting the so deviated electrons, said collecting means including a first pick-up means positioned to receive said electrons when they are unaffected by said space pattern of fields and a second pick-up means positioned to receive the electrons displaced from said first pick-up means in function of the magnetic condition of said fields and means for utilizing said collected electrons.

15. An apparatus for translating magnetic signals to electrical signals which comprises an envelope, a target means positioned in a predetermined area of said envelope, said target means having a face, a magnetic condition space pattern record, said record being positioned so that its magnetic fields permeate said target means and establish a pattern of magnetic fields on said face, means for producing an electron beam within said envelope, means for subjecting consecutive areas of said magnetic fields to said beam so as to cause the electrons of said beam to alter their paths in dependence on the magnetic condition of said pattern of fields, means for focusing and directing said electron beam from said target means to a collecting means, said focusing and directing means adapted to have an object focal plane and an equatorial mid-plane, said target means positioned at said object focal plane, said collecting means positioned in said equatorial mid-plane and means for utilizing the electrons collected by said collecting means.

16. An apparatus for translating magnetic signals to electrical signals as claimed in claim 15 wherein said means for producing said electron beam comprises means for adapting said face of said target electrode for the emission of a stream of electrons when impinged upon by a beam of radiant energy and including means for forming and conveying said beam of radiant energy to said face.

17. An apparatus for translating magnetic signals to electrical signals which comprises an envelope, a target means positioned in a predetermined area of said envelope, said target means having a face, a magnetic condition space pattern record, said record being positioned so that its magnetic fields permeate said target means and establish a pattern of magnetic fields on said face, means for producing an electron beam within said envelope, means for subjecting consecutive areas of said magnetic fields to said beam so as to cause the electrons of said beam to alter their paths in dependence on the magnetic condition of said pattern of fields, means for focusing and directing said beam from said target means to a collecting means, said focusing and directing means adapted to have an object focal plane and an image focal plane, said target means positioned at said object focal plane, said collecting means positioned at said image focal plane; and means for utilizing the electrons collected by said collecting means.

18. An apparatus for translating magnetic signals to electrical signals as claimed in claim 17 wherein said means for producing said electron beam comprises means for adapting said face of said target electrode for the emission of a stream of electrons when impinged upon by a beam of radiant energy and including means for forming and conveying said beam of radiant energy to said face.

19. An apparatus for translating magnetic signals to electrical signals which comprises an envelope, a target means sealed into a predetermined area of said envelope, said target means having a face, a magnetic space pattern record, said record being positioned so that its magnetic fields permeate said target means and establish a pattern of magnetic fields on said face, means for producing an electron beam within said envelope, means for subjecting consecutive .areas of said fields to said beam so as to cause the electrons of said beam to alter their paths in dependence on the magnetic condition of said pattern of fields, means for collecting said beam after said beam has traversed said fields, said collecting means being adapted to have a resistive gradient from any point thereof to any other point thereof whereby a change in current of said beam is produced as a function of said deviated electrons; and means for utilizing said collected electrons.

References Cited in the file of this patent UNITED STATES PATENTS 2,165,307 Skellett July 11, 1939 2,433,941 Weimer Jan. 6, 1948 2,550,759 Bezy May 1, 1951 2,563,197 Sziklai Aug. 7, 1951 2,657,378 Gray Oct. 27, 1953 

